In centrifuges, a sample solution is attached to a rotor that is spun at high rotational speeds to centrifugally separate the components based upon differences in molecular weight. Centrifugal force is dependent upon the mass of the component, the rotational speed of the rotor and the distance of the sample solution from the rotational axis.
A principal goal in the design of centrifuge systems is directed toward improving the separation/sedimentation of sample components. This typically requires increasing the centrifugal force experienced by the sample, necessitating increased rotational speed or rotor size. However, as the centrifugal force increases, the ability to contain the sample decreases.
For example, as discussed in U.S. Pat. No. 3,819,111 to Romanauskas et al., while undergoing centrifugation, seals of receptacles containing samples may become compromised, resulting in liquid emerging therefrom and filling the centrifuge housing. To retain the liquid, a cover is disposed over the rotor which includes a downwardly depending skirt having a portion which seats against a peripheral rim of the rotor. The cover includes an outwardly facing shoulder, facing a surface of the rotor having a complementary shape. The surface of the cover, positioned opposite to the shoulder, is angled to extend upwardly and outwardly away from the center of the rotor, defining an angled member. An outwardly facing peripheral groove is formed in the angled member which is adapted to receive an O-ring. The O-ring presses against the rotor upon tightening of the cover on the same. During centrifugation, the cover presses downwardly against the rotor, increasing the seal between the cover and the rotor. Disposed in the cover, opposite to the angled member, is a recess in which liquid from the receptacles is contained during centrifugation.
U.S. Pat. No. 3,901,434 to Wright discloses a lid seal for centrifuge rotors, having receptacles therein, which overcomes the drawback of Romanauskas et al. The cover includes, inter alia, a fluid release opening to form what amounts to a pressure relief valve. The release opening communicates with a seal-ring groove in the cover and guards against possible expulsion of the seal ring from the seal-ring groove in the event that one or more of the containers should rupture. This also reduces the fluid pressure acting upon the cover, thereby reducing the probability that the same would bend the cover upwardly away from the receptacles.
U.S. Pat. No. 4,202,487 to Edwards discloses a rotor lid comprising, inter alia, a flat circular disc having a thicker outer perimeter which is designed to mate with the outer perimeter of the rotor. The rotor has an annular recess between a central raised portion and an outer raised perimeter area. The lid utilizes a depending threaded stud to engage a threaded aperture centered on the rotor. An O-ring is located between the outer raised perimeter area of the rotor and the enlarged rim of the lid. The configuration of the enlarged rim on the lid results in a downward force on the O-ring during centrifugation, holding the same in place.
U.S. Pat. No. 4,484,906 to Strain discloses a shell type centrifuge rotor including, inter alia, an upper shell and a lower shell, both of which are connected to a central hub disposed therebetween. The upper shell has a substantially frustoconical shape and a recessed top surface. The top surface has a form generally corresponding to the interior of an inverted frustum. A plurality of samples are disposed in a circular locus in the top of the rotor. The lower shell of the rotor has a bottom formed with upturned inwardly sloping conical sides so that, even if a tube ruptures, the contents of the tube will be retained in the lower shell.
U.S. Pat. No. 5,484,381 to Potter discloses a rotor adapted for use in a non-evacuated chamber that includes, inter alia, a plurality of liquid-capturing holes, each of which includes an opening. Each opening lies radially outboard of a circular locus defined by points on each of the plurality of container-receiving cavities formed in the rotor.
U.S. Pat. No. 4,196,844 to Jacobson discloses a closing structure for an evacuated centrifuge chamber including, inter alia, a door which is slidable horizontally toward and away from a closed position and a retaining member disposed above the door. The retaining member limits upward movement of the door. A side member surrounds the closed door on three sides to contain shrapnel that results from rotor failure. A flange extends downwardly from the door on the remaining side to prevent shrapnel from traveling through the lid-housing interface, thereby preventing shrapnel from exiting the centrifuge.
The aforementioned centrifuges are typically directed toward containing liquid matter within the rotor and are not directed toward containing both particulate, such as shrapnel, and liquid matter within the centrifuge system. This represents a major drawback with the prior art centrifuge designs, because many countries require centrifuges to control the distance that both particulate and liquid matter can travel from the centrifuge when the rotor fails. For example, in the International Electrotechnical Commission, Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use, 1010-2-020 (1st ed. 1992), a centrifuge must prevent penetration by shrapnel upon initial and subsequent impact. Shrapnel larger than 1.5 mm in size must not escape through the lid-housing interface, and shrapnel and liquid less than 1.5 mm in size must not travel over 300 mm from the centrifuge.
It is an object, therefore, of the present invention to provide a lightweight containment system for a centrifuge capable of reducing the amount of both liquid and shrapnel that escapes from the centrifuge housing in the event of rotor failure.